Trust helps assure that one party will not take advantage of the vulnerability of the other during or after the transaction. Trust acts as an informal control mechanism that reduces friction, limits opportunistic behaviors, minimizes the need for bureaucratic structures, encourages future transactions, and helps build long-term relationships. In contrast, lack of trust may require full disclosure of otherwise commonly accepted transaction rules in the form of extensive legal contracts, leading to greater transaction costs and lower business efficiencies.

An integrative definition of trust is the following: Trust is "the willingness of a party [trustor] to be vulnerable to the actions of another party [trustee] based on the expectation that the other [trustee] will perform a particular action important to the trustor, irrespective of the ability to monitor or control that other party [trustee]. In consumer-based e-commerce, consumers (users) are the trustors and online firms are the trustees, since users provide sensitive information such as e-mail addresses, credit card numbers, and personal preferences to these firms and are hence vulnerable to firm behavior.